PG&E replaced San Bruno pipelines in 1993, but stopped one block short of doomed section

PG&E officials were so concerned about the risk of their natural gas transmission lines bursting during an earthquake that, in 1993 and 1994, they replaced five miles of aging underground steel pipes in San Bruno.

But the utility's construction crews ended the job less than 300 yards from Glenview Drive and Earl Avenue, the site of the deadly explosion that killed eight people last September, new documents released by the National Transportation Safety Board show.

Had PG&E funded a more complete seismic safety upgrade of the 1956-era pipeline, known as line 132, its workers 17 years ago would have dug up and replaced the flawed section that exploded -- a section that federal investigators later found contained more than 150 welding defects.

"Oh my God. It's stunning. It's really amazing," said Bill Magoolaghan, whose house was damaged in the blast. "But for another block of digging, and we wouldn't have lost eight neighbors."

PG&E spokesman Joe Molica confirmed that the seismic upgrade work spelled out in the 1993 documents did occur.

"The work was completed," he said. "It was done just as the documents show."

A central question remained Thursday: If PG&E geologists and engineers were concerned about damage to their gas transmission pipelines in San Bruno neighborhoods from a major quake on the San Andreas Fault, which they called "the greatest seismic hazard to our pipelines on the San Francisco Peninsula," why did they only replace some of those lines with newer, thicker steel and leave other aging lines directly adjacent to them untouched?

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Still a mystery

Molica said he doesn't know why PG&E did not replace the rest of line 132 as part of the job. PG&E documents show that a section of line 132 at Glenview Drive and Plymouth Way was replaced, and a section of line 109, at Glenview Drive and San Bruno Avenue, less than half a mile away from the blast site, also was replaced.

In fact, lines on both sides of the section that blew up, destroying 38 homes, were replaced.

"I'm sorry I don't have more," Molica said. "We are in the middle of doing a comprehensive records review. This is a massive undertaking."

Molica added:

"Our geosciences department is focused on seismic risk. The segment involved in this terrible tragedy was not a part of this project list. We are now undertaking a rigorous and comprehensive evaluation of every aspect of gas pipeline safety at PG&E. Safety is our highest responsibility."

The documents were among thousands of pages of records released Tuesday by the NTSB.

They highlight how PG&E officials had major concerns about pipelines and earthquakes in San Bruno.

A quake on the San Andreas Fault, which runs along Skyline Boulevard on San Bruno's western edge, could cause a 10-foot ground displacement, PG&E officials wrote.

The same document summarizing the project noted that "replacement priorities are based on age, construction factors, condition of the pipe, and exposure to seismic hazards." It said that an area "of possible slope instability" was at Glenview Drive at Earl Avenue, the site of the blast, and also at San Bruno Avenue between Glenwood and Alpine.

Thicker pipe installed

To install the new pipelines, PG&E crews dug trenches 6 feet deep and surrounded the new gas mains with sand. The new steel pipe was .5 inches thick, considerably stronger than the .375-inch-thick pipe that was left in the ground and exploded.

The new route to replace line 109, moving it off Skyline Boulevard and further away from the fault, sent the pipeline from Hickey Boulevard in Daly City along Interstate 280 and up San Bruno Drive. The work to replace sections of line 132, the line that exploded, was more limited, mostly done near Claremont and Skyline drives. The new lines "should last for another 80 to 100 years" PG&E said in a 1993 notice to customers.

Work on the section of line 132 closest to the September explosion site began in January 1994 and finished in April 1994.

"If they are replacing old pipe with new pipe, why not just do the whole job?," Magoolaghan asked. "It seems like bad decision making, or bad luck."